Add support for all libtest flags

[roman-kashitsyn]

Raclette should understand all the options that libtest can handle so that Raclette and libtest targets can always be run with the same command. Libtest options:

Options:
        --include-ignored
                        Run ignored and not ignored tests
        --ignored       Run only ignored tests
        --force-run-in-process
                        Forces tests to run in-process when panic=abort
        --exclude-should-panic
                        Excludes tests marked as should_panic
        --test          Run tests and not benchmarks
        --bench         Run benchmarks instead of tests
        --list          List all tests and benchmarks
    -h, --help          Display this message (longer with --help)
        --logfile PATH  Write logs to the specified file instead of stdout
        --nocapture     don't capture stdout/stderr of each task, allow
                        printing directly
        --test-threads n_threads
                        Number of threads used for running tests in parallel
        --skip FILTER   Skip tests whose names contain FILTER (this flag can
                        be used multiple times)
    -q, --quiet         Display one character per test instead of one line.
                        Alias to --format=terse
        --exact         Exactly match filters rather than by substring
        --color auto|always|never
                        Configure coloring of output:
                        auto = colorize if stdout is a tty and tests are run
                        on serially (default);
                        always = always colorize output;
                        never = never colorize output;
        --format pretty|terse|json
                        Configure formatting of output:
                        pretty = Print verbose output;
                        terse = Display one character per test;
                        json = Output a json document
        --show-output   Show captured stdout of successful tests
    -Z unstable-options Enable nightly-only flags:
                        unstable-options = Allow use of experimental features
        --report-time [plain|colored]
                        Show execution time of each test. Awailable values:
                        plain = do not colorize the execution time (default);
                        colored = colorize output according to the `color`
                        parameter value;
                        Threshold values for colorized output can be
                        configured via
                        `RUST_TEST_TIME_UNIT`, `RUST_TEST_TIME_INTEGRATION`
                        and
                        `RUST_TEST_TIME_DOCTEST` environment variables.
                        Expected format of environment variable is
                        `VARIABLE=WARN_TIME,CRITICAL_TIME`.
                        Durations must be specified in milliseconds, e.g.
                        `500,2000` means that the warn time
                        is 0.5 seconds, and the critical time is 2 seconds.
                        Not available for --format=terse
        --ensure-time   Treat excess of the test execution time limit as
                        error.
                        Threshold values for this option can be configured via
                        `RUST_TEST_TIME_UNIT`, `RUST_TEST_TIME_INTEGRATION`
                        and
                        `RUST_TEST_TIME_DOCTEST` environment variables.
                        Expected format of environment variable is
                        `VARIABLE=WARN_TIME,CRITICAL_TIME`.
                        `CRITICAL_TIME` here means the limit that should not
                        be exceeded by test.


The FILTER string is tested against the name of all tests, and only those
tests whose names contain the filter are run.

By default, all tests are run in parallel. This can be altered with the
--test-threads flag or the RUST_TEST_THREADS environment variable when running
tests (set it to 1).

All tests have their standard output and standard error captured by default.
This can be overridden with the --nocapture flag or setting RUST_TEST_NOCAPTURE
environment variable to a value other than "0". Logging is not captured by default.